Process for the transmission of sounds and for their reception in the proper volume



Sept. 5, 1939. J. J. L -AUB I PRocEss -FoR THE TRANSMISSION oF souNDsAND FOR.

THEIR RECEPTION IN THE PROPER voLUNE Filed Aug. 5, 1936 NN www. RN. L

.anima wm uw QN EN INVENTOR. y. Gau

BY acoba y @www ATTORNEY.

Patented Sept. 5, 1939 y UNITED STATES PATENT ol-FlcEg PROCESS FOR. THETRANSVIISSION F SOUNDS AND FOR THEIRI RECEPTION IN Y THE PROPER VOLUIVIEJacobo J. Laub, Hamburg, Germany Application August 5, 1936,- Serial No.94,415

` In Germany August 5, 1935 This invention relates to a method and asys- In particular, this application is a continuatem for transmittingand receiving sound in tion in part of application Serial Number682,922, proper auditory manner. i'lled July "'31, 1933, and issued intoPatent No.

If a concert or a musical play performed on 2,110,444, of'which I am aco-inventor. I a stage is picked up by a microphone and trans- Accordingto my invention the sounds of dif- I mitted to another place where it isreproduced ferent origin are picked up by microphones suitabyloudspeakers or head telephones, the proper Vbly positioned relative tothesource of such difacoustical and therefore musical effect is mostlyferent sounds, and the electrical vimpulses of lost. Therefore, it hasbeen suggested to install sound frequency produced by the microphones l0a plurality of microphones on the stage, in difare modulated uponcarrierv waves of a frequency 10 ferent positions, and to conduct thesounds substantially exceeding 60 kilocycles. 'I'he impicked up lby themicrophones to individual pulses originated in the microphones may betransmission lines, and ultimately to receivers amplified modestly, ifnecessary, beforemoduindividually connected to those vtransmissionlating them upon the high frequency carrier l5 lines. 'I'he receiversincluded loudspeakers orv wave. At the place of reproduction the soundl5 head telephones. Thereby the reproduction of impulses are demodulatedfrom the carrier waves the original music was improved. Different andreproduced in suitable devices, such as loudmethods and systems based onthis principal speakers or head telephones. idea have been developedsince.' One system The invention may be explained more in detail Ycopies the position of the ears of a listener by with reference to thedrawing in which a transm arranging two microphonesnear the place or'mitting system according to my invention is stage where the orchestra orthe musical play shown but in a diagrammatic way only. are performed,while other systems arrange In the drawing, 2 is a stage for anorchestra microphones in places where sounds of different 1 infront ofwhich microphones 3 and 4 are posicharacter are originated, such astrumpets, tioned. Any number of microphones may be g5 violins, singers,etc., transmitting the sound used, and they may be positioned either infront Waves through different channels to the place of the stage or onthe stage proper, e. g., near the of reception. If two pick-upmicrophones are musical instruments of different character. The used,copying the position of the ears of a sounds picked up bythe'microphones are trans- 80 listener, the reproduction in the place ofrecepformed by them intoelectrical impulses which 30 tion is to be donein such manner that the are amplified in the amplifiers 5 and 6,respeclistener receives the sound adequately. If a tively, if desired,and modulatedii the moduplurality of microphones is positioned near thelators 1 and 8 upon carrier wavesfof sufficiently place of Aorigin ofdifferent sounds, individual different frequencies originated by theoscillators different loudspeakers are used in the place of 9 and I0.'I'he frequency of these carrier waves 35 reproduction which reproducethe different is in any case substantially higher than 60 kilosounds.cycles, corresponding to a wave length of 'less It is an object of theinvention to simplify than 5000 meters. As shown in the drawing, thosemethods and systems independently of the modulated carrier waves passband pass- 40 whether they are used for so-called binaural or filters Iland I2, respectively, and then pass 40 for multi-channel transmission.along the single transmission line i3. The

It is another object of the invention to transtransmission line mayconsist of an open-air or mit sounds deriving from a plurality ofsources cable wire- The modulated carrier waves of by means of apparatusused in ordinary broad'- different frequencies may be led, however,along casting along existing open-air or cable wires. differenttransmission lines. Each modulated .45

It is still another object of the invention to carrier Wave may then goalong a different opentransmit simultaneously sounds of different airwire, or pair of wires insulated against each origin along open-air orcable wires without other withinV the same cable, or arranged inaffecting other transmissions through the same different cables.

channels within ordinary broadcast-range of The reproduction may beperformed to an 50 `v carrier waves. auditorium I4 by means ofloudspeakers l5 and It is still another object of the invention to i6,arranged in front of that auditorium in simitransmit simultaneouslysounds of different lar relativeposition as the microphones are aroriginalong open-air orcable wires in a simple, ranged in front of theorchestra. Thus, the

56 eflicient and undisturbed manner. loudspeaker I6 is controlled by thesounds picked `arated by means of filter I1.

are demodulated in the demodulators 2| and 22,

and the demodulated sound waves are conducted to the loudspeakers I5 andIB. Low frequency amplifiers, not shownin the drawing, may be appliedthough high frequency amplification is preferred.

A number of repeaters, including one shown at 23, may be arranged alongthe transmission line, if necessary.

Instead of a stage for an orchestra there may' be arranged a stage for amusical'play, for speeches, for broadcasting purposes of any kind,including news, publicity and information.

By using the high frequency range according to this invention,transmission lines can be saved and existing ones, such .as open-airlines and cable lines, may be used. If a plurality of lines is used,each of them can be utilized for transmitting one or more differentsounds modulated upon sufficiently different high frequency (or shortwave) carriers (channels). Thereby, e. g., a concert can be transmittedand reproduced to the highest degree of fidelity because a. great numberof carriers can be utilized along one line, and therefore, if aplurality of lines is used, the number of carriers can be multipliedaccordingly.

Furthermore, if, e. g., concert music is transmitted it is imperative ingeneral to transmit a wide frequency band. That is difficult, if at allpossible, when carriers of ordinary broadcasting range are used. If,however, carriers of the high frequency range suggested by my inventionare used, wide low frequency bands can be transmitted because those widelow frequency bands can easily be modulated upon carriersof highestfrequency. As it is known to the' art, not the abs'olute width of a lowfrequency band, Ibut the ratio of its width to the frequency of thecarrier is decisive. With my invention, amplification of the soundspicked up by the microphone is either not needed or only to a smallde'gree. Thus, for instance, a single tube amplifier will, as a rule,suice. Furthermore, amplifiers having a flat characteristic and a Widefield of amplitude, insuring a regular amplification, are preferred.Amplifiers with steep characteristics and a high degree of amplificationare undesirable, as a rule. The tubes of the modulator can be controlledby relatively small amplitudes of the sound waves if carriers of as highfrequency as contemplated by my invention are concerned, and thisaccounts for the relatively small ampliiication of the low frequencieswhich satises my invention. y

At the place of reproduction, amplification of the high frequency wavesis advisable. Such amplification may be obtained in the equalizers, ordemodulators, shown in the drawing, and low frequency amplifiers may bedispensed with.

By using solely amplifiers for the carrier, a high degree of fidelity ofreproduction is assured. If a single line for the transmission is used,carrier waves must be of sufliciently different high frequency. If aplurality of lines and a. single one for each carrier is used, thelatter ones may be altogether of the same high frequency. There will beno need for anticipating interference, this having been proven by tests.

If a single line is used and e. -.g. two carriers are transmitted, asshown in the drawing, one carrier may be e. g. of 300 and the other oneof 160 kilocycles. Instead of the loudspeakers shown any other soundreproducing device may be used, such as head telephones.

What I claim is:

1. A method of picking up, transmitting, receiving and reproducingsounds of different character or origin and covering a widefrequencyband, comprising the steps of transforming said sounds into electricalimpulses by means of a number, including two as a minimum, ofmicrophones arranged to pick up said individual sounds of differentcharacter or origin, slightly amplifying and modulating said impulses bymeans continuously in circuit individually upon individual carriers of ahigh frequency capable of being modulated by a wide frequency band andexceeding 60 kilocycles, transmitting said modulated carriers along atleast one existing aperiodic non-concentric line for transmitting othercommunications within lower frequency ranges to the place. of reception,demodulating said impulses individually from said individual carriers,and retransforming individually said demodulated impulses intoacoustical impulses by means continuously in circuit.

2. In a method as described in claim 1, amplifying said modulatedcarriers on the place of reception by means of amplifiers having a flatcharacteristic.

3. In a method as described in claim 1, amplifying by means of wide bandamplifiers individually said modulated carriers While passing theirchannel from ,the place of transmission to the one of reception.

4. A system for transmitting and receiving sound impulses of differentcharacter or origin and covering a wide frequency band, comprising anumber, including two as a minimum, microphone groups, each of saidgroups comprising at least one microphone and arranged for picking upsound of individual `character or origin, means for generating highfrequency carrier waves in a number corresponding to the one of saidgroups, and of a frequency capable of being modulated by a widefrequency band and exceeding 60 kilocycles, means continuously incircuit for slightly amplifyingand modulating said sound impulsesoriginating from each of -said microphones individually upon a carrierwave each, means for individually receiving said modulated carrierwaves, at 1eastone existing aperiodic non-concentric line fortransmitting other communications within lower frequencyrangesconnecting said transmission and receiving stations for guiding saidmodulated carriers, means for demodulating therefrom said soundimpulses, and means continuously in circuit for reproducing said latterones.

5. A system for transmitting and receiving sound impulses of differentcharacter or origin and covering a wide frequency band, comprising anumber, including two as a minimum, microphone groups, each of saidgroups comprising at least one microphone and arranged for picking upsolmd of individual character or origin, means for generating highfrequency. carrier waves in a number corresponding to the one of saidgroups and of a frequency capable of being modulated by a Wide frequencyband and exceeding 60 kilocycles, means continuously in circuit formodulating sound impulses originating from each of said microphonesindividually upon a carrier Wave each, at least one channel common to atleast two of said carriers, means for individually receiving saidmodulatedv carrier Waves, at least one existing aperiodic non-concentricline for transmitting other communications within lower frequency ranges.connecting said transmission and receiving stations for guiding saidmodulated carriers, wide band pass-lters for separating said carriers,means for demodulating therefrom said sound impulses, and spaced meanscontinuously

